1. What is the RPM Gear Ratio Formula?

The RPM Gear Ratio formula calculates engine revolutions per minute based on vehicle speed, gear ratio, and tire circumference. It's essential for automotive performance tuning and gear selection.

2. How Does the Calculator Work?

The calculator uses the RPM formula:

Where:

• \( S \) — Vehicle speed (mph)
• \( GR \) — Gear ratio
• \( C \) — Tire circumference (inches)
• 336 — Constant conversion factor

Explanation: The formula converts vehicle speed to engine RPM by accounting for the gear reduction and tire size.

3. Importance of RPM Calculation

Details: Accurate RPM calculation is crucial for proper gear selection, fuel efficiency optimization, and preventing engine over-revving or lugging.

4. Using the Calculator

Tips: Enter vehicle speed in mph, gear ratio as a decimal value, and tire circumference in inches. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is the constant 336 used in the formula?
A: The constant 336 combines conversion factors for units (mph to inches per minute) and accounts for the relationship between tire rotation and engine rotation.

Q2: How do I measure tire circumference?
A: Measure the distance the tire travels in one complete revolution, or calculate it from tire size specifications using standard formulas.

Q3: What is a typical gear ratio range?
A: Gear ratios typically range from 2.5:1 to 4.5:1 for final drive ratios, with transmission gear ratios adding additional multiplication.

Q4: Does this work for all vehicle types?
A: The formula works for most wheeled vehicles but may need adjustment for vehicles with different drive configurations or torque converters.

Q5: How accurate is this calculation?
A: The calculation provides a theoretical RPM that's typically within 2-3% of actual values, assuming no tire slip or transmission losses.